Not Applicable
1. Field of the Invention
The invention relates to a novel process for the manufacture of functionalized polyphenylene ether resins through redistribution with a functionalized phenolic compound in the polyphenylene ether resin polymerization reaction solution without the addition of an added redistribution catalyst or promoter.
The invention also relates to the functionalized polyphenylene ether resin made by the process as well as blends and articles containing the functionalized polyphenylene ether resin made by the process.
2. Brief Description of the Related Art
Polyphenylene ether resins (hereinafter xe2x80x9cPPExe2x80x9d) are commercially attractive materials because of their unique combination of physical, chemical, and electrical properties. Furthermore, the combination of PPE with other resins provides blends, which result in additional overall properties such as chemical resistance, high strength, and high flow.
One obstacle to blending PPE with other resins is the lack of compatibility between the resins. This lack of compatibility often manifests itself as delamination and/or poor physical properties such as, for example, poor ductility. One useful method known in the art to improve the compatibility between resins is to generate reaction products between the polymers that will act as compatibilizers for the resins. The reaction products are often thought of as copolymers of the resins.
One challenge in preparing the aforementioned reaction products is the need for reactive sites on the resins that will lead to the formation of reaction products. Some polymers such as polyamides inherently possess both amine and carboxylic acid endgroups that can readily undergo reaction with another resin containing a wide variety of possible reactive moieties. Polymers like PPE contain primarily phenolic endgroups and are in general not sufficiently reactive to result in the aforementioned reaction products in commercially feasible processes.
It should be apparent that methods and processes to introduce functionality into PPE are highly sought after. Redistribution, also known as equilibration, of phenolic compounds containing at least one functional moiety has been shown to afford PPE having desirable functionality. In the redistribution reaction of PPE with phenolic compounds, the PPE are usually split into shorter units with the phenolic compound incorporated in the PPE.
In the redistribution reactions illustrated in the art, the PPE is dissolved in a solvent with the phenolic compound and a catalyst, optionally with a promoter, is add to the reaction mixture. After heating at elevated temperatures, generally between 60xc2x0 C. and 80xc2x0 C., the redistributed PPE is isolated.
In order to utilize the redistribution technology in a commercially feasible manner, a process was needed that would minimize the need for additional processes, reaction vessels, and handling of PPE. It should be apparent that a process that would take advantage of the PPE polymerization process and associated mechanical equipment would be extremely advantageous.
The needs discussed above have been generally satisfied by the discovery of a process for preparing a functionalized PPE through redistribution with a phenolic compound prior to isolation of the PPE from the oxidative coupling reaction mixture and without the addition of a catalyst or a promoter. The oxidative coupling reaction conditions can be adjusted to afford sufficient in situ catalyst for the redistribution reaction.
The description that follows provides further details regarding various embodiments of the invention.
Not applicable
This invention provides for a process for the preparation of low molecular weight PPE, preferably about 0.05 dl/g and 0.5 dl/g, preferably about 0.08 dl/g and 0.4 dl/g, more preferably having an intrinsic viscosity between about 0.08 dl/g and 0.16 dl/g, by oxidative coupling at least one monovalent phenol species, preferably at least a portion of which have substitution in at least the two ortho positions and hydrogen or halogen in the para position, to produce a PPE having an intrinsic viscosity of greater than about 0.16 dl/g as measured in chloroform at 25xc2x0 C. using an oxygen containing gas and a complex metal-amine catalyst, preferably a copper (I)-amine catalyst, as the oxidizing agent, redistributing at least one additional phenol species to produce a PPE having an intrinsic viscosity within the range of about 0.05 dl/g and 0.5 dl/g, preferably about 0.08 dl/g and 0.4 dl/g, more preferably about 0.08 dl/g to about 0.16 dl/g, and extracting at least a portion of the metal catalyst as a metal-organic acid salt with an aqueous containing solution, and isolating the PPE through devolatilization of the reaction solvent. In one embodiment, the additional phenol species comprises a functionalized phenol species. In another embodiment, the additional phenol species is equilibrated into the PPE without additional initiator.
The PPE employed in the present invention are known polymers comprising a plurality of structural units of the formula 
wherein each structural unit may be the same or different, and in each structural unit, each Q1 is independently halogen, primary or secondary lower alkyl (i.e., alkyl containing up to 7 carbon atoms), phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and each Q2 is independently hydrogen, halogen, primary or secondary lower alkyl, phenyl, haloalkyl, hydrocarbonoxy or halohydrocarbonoxy as defined for Q1. Most often, each Q1 is alkyl or phenyl, especially C1-4 alkyl, and each Q2 is hydrogen.
Both homopolymer and copolymer PPE are included. The preferred homopolymers are those containing 2,6-dimethyl-1,4-phenylene ether units. Suitable copolymers include random copolymers containing such units in combination with (for example) 2,3,6-trimethyl-1,4-phenylene ether units. Also included are PPE containing moieties prepared by grafting vinyl monomers or polymers such as polystyrenes and elastomers, as well as coupled PPE in which coupling agents such as low molecular weight polycarbonates, quinones, heterocycles and formals undergo reaction in known manner with the hydroxy groups of two poly(phenylene ether) chains to produce a higher molecular weight polymer, provided a substantial proportion of free OH groups remains.
The PPE are typically prepared by the oxidative coupling of at least one monohydroxyaromatic compound such as 2,6-xylenol, 2,3,6-trimethylphenol, or mixtures of the foregoing. Catalyst systems are generally employed for such coupling and they typically contain at least one heavy metal compound such as a copper, manganese, or cobalt compound, usually in combination with various other materials.
It will be apparent to those skilled in the art from the foregoing that the PPE contemplated in the present invention include all those presently known, irrespective of variations in structural units or ancillary chemical features.
The polymerization of the phenolic monomer may be carried out by adding the phenolic monomer or monomers to a suitable reaction solvent and preferably, a copper-amine catalyst. It is preferred to carry out the polymerization in the presence of a cupric salt-secondary amine catalyst such as, for example, cupric chloride and di-n-butylamine. The polymerizations are advantageously carried out in the presence of an inorganic alkali metal bromide or an alkaline earth metal bromide. The inorganic bromides may be used at a level of from about 0.1 mole to about 150 moles per 100 moles of phenolic monomer. These catalyst materials are described in U.S. Pat. No. 3,733,299 (Cooper et al.). Tetraalkylammonium salts may also be employed as promoters if desired. These promoters are disclosed in U.S. Pat. No. 3,988,297 (Bennett et al.).
The primary, secondary or tertiary amine components of the catalyst complex generally correspond to those disclosed in U.S. Pat. Nos. 3,306,874 and 3,306,875 (Hay). Illustrative members include aliphatic amines, including aliphatic mono- and di-amines, where the aliphatic group can be straight or branched chain hydrocarbon or cycloaliphatic. Preferred are aliphatic primary, secondary and tertiary monoamines and tertiary diamines. Especially preferred are mono-, di- and tri(lower) alkyl amines, the alkyl groups having from 1 to 6 carbon atoms. Typically, there can be used mono-, di- and tri-methyl, ethyl, n-propyl i-propyl, n-butyl substituted amines, mono- and di-cyclohexylamine, ethylmethyl amine, morpholine, N-(lower) alkyl cycloaliphatic amines, such as N-methylcyclohexylamine, N,Nxe2x80x2-dialkylethylenediamines, the N,Nxe2x80x2-dialkylpropanediamines, the N,N,N,xe2x80x2-trialkylpentanediamines, and the like. In addition, cyclic tertiary amines, such as pyridine, alpha-collidine, gamma picoline, and the like, can be used. Especially useful are N,N,Nxe2x80x2,Nxe2x80x2-tetraalkylethylenediamines, butane-diamines, and the like.
Mixtures of such primary, secondary and tertiary amines may be used. A preferred mono alkyl amine is n-butyl amine; a preferred dialkyl amine is di-n-butyl amine; and a preferred trialkyl amine is triethylamine. A preferred cyclic tertiary amine is pyridine. The concentration of primary and secondary amine in the reaction mixture may vary within wide limits, but is desirably added in low concentrations. A preferred range of non-tertiary amines comprises from about 2.0 to about 25.0 moles per 100 moles of monovalent phenol. In the case of a tertiary amine, the preferred range is considerably broader, and comprises from about 0.2 to about 1500 moles per 100 moles of monovalent phenol. With tertiary amines, if water is not removed from the reaction mixture, it is preferred to use from about 500 to about 1500 moles of amine per 100 moles of phenol. If water is removed from the reaction, then only about 10 moles of tertiary amine, e.g., triethylamine or triethylamine, per 100 moles of phenol need be used as a lower limit. Even smaller amounts of tertiary diamines, such as N,N,Nxe2x80x2Nxe2x80x2-tetramethylbutanediamine can be used, down to as low as about 0.2 mole per 100 moles of phenol.
Typical examples of cuprous salts and cupric salts suitable for the process are shown in the Hay patents. These salts include, for example, cuprous chloride, cuprous bromide, cuprous sulfate, cuprous azide, cuprous tetramine sulfate, cuprous acetate, cuprous butyrate, cuprous toluate, cupric chloride, cupric bromide, cupric sulfate, cupric azide, cupric tetramine sulfate, cupric acetate, cupric butyrate, cupric toluate, and the like. Preferred cuprous and cupric salts include the halides, alkanoates or sulfates, e.g., cuprous bromide and cuprous chloride, cupric bromide and cupric chloride, cupric sulfate, cupric fluoride, cuprous acetate and cupric acetate. With primary and secondary amines, the concentration of the copper salts is desirable maintained low and preferably varies from about 0.2 to 2.5 moles per 100 moles of monovalent phenol. With tertiary amines, the copper salt is preferable used in an amount providing from about 0.2 to about 15 moles per 100 moles of the monovalent phenol.
Cupric halides are generally preferred over cuprous halides for the preparation of the copper amine catalyst because of their lower cost. The use of the copper (I) species also greatly increases the rate of oxygen utilization in the early stages of the polymerization reaction and the lower oxygen concentration in the head space of the reactor helps in reducing the risk of fire or explosion in the reactor. A process for the preparation and use of suitable copper-amine catalysts is in U.S. Pat. No. 3,900,445 (Cooper et al.).
In the practice of the invention, the catalyst (also known as an initiator) for the redistribution reaction is preferably generated in situ during the oxidative coupling process. Backward dimer, tetramethyldiphenylquinone (TMDQ), is normally made during coupling of 2,6-dimethylphenol and is a preferred catalyst. Other diphenylquinones may also be present depending on the phenolic species being oxidatively coupled.
Reaction conditions that favor generation of the backward dimer are preferred and can be readily controlled. When the level of monomer is increased during the early stages of oxidation, higher levels of TMDQ are produced. Likewise, a slower initial reaction rate with the copper (I) based catalyst also results in an increased accumulation of unreacted monomer and an increase in the amount of TMDQ produced. The copper amine ratio affects the amount of TMDQ generated with a higher ratio of amine to copper favoring an increase in the amount of TMDQ. Additionally, allowing the reaction mixture to heat, preferably from the reaction exotherm, also results in higher levels of TMDQ. Generally, the reaction mixture is maintained between about 30xc2x0 and 45xc2x0 C., however allowing the temperature to increase to even 50xc2x0 C. results in an increase in the level of TMDQ. Preferably the level of catalyst is less than 10% by weight with respect to the PPE.
Numerous studies conducted to determine conditions that can lead to increased levels of backward dimer (e.g., TMDQ) during the oxidative coupling process have resulted in a number of other unexpected factors that affect the formation of backward dimer. First, increasing the ratio of phenolic monomer to solvent (e.g., 2,6-xylenol:toluene ratio) leads to higher backward dimer ratios as does a high addition rate of phenolic monomer to the reaction mixture. As previously discussed, increases in the reactor temperature also leads to increased levels of backward dimer. Finally, running the oxidative coupling at a lower percentage of oxygen in the reactor (i.e. a lower phenolic to oxygen ratio) also leads to increased amounts of backward dimer.
If no additional functionalized phenolic compound is added at the equilibration step of the process, the TMDQ (or any other backward dimer) becomes incorporated into the PPE and can lead to a high hydroxyl PPE. It should be clear that the present invention also includes processes to increase the hydroxyl level on PPE by increasing the level of backward dimer (e.g., TMDQ) during the oxidative coupling process and incorporating at least a portion of the TMDQ through redistribution (i.e. equilibration). For example, a PPE oxidative coupling reaction that has a TMDQ level of about six weight percent based on the weight of the PPE at the end of reaction had a hydroxyl number of about 360 xcexcmol/g after equilibration.
The polymerization reaction is preferably performed in a solvent. Suitable solvents are disclosed in the above-noted Hay patents. Aromatic solvents such as benzene, toluene, ethylbenzene, xylene, and o-dichlorobenzene are especially preferred, although tetrachloromethane, trichloromethane, dichloromethane, 1,2-dichloroethane and trichloroethylene may also be used. The weight ratio between solvent and monomer is normally in the range from 1:1 to 20:1, i.e., up to a maximum 20-fold excess of solvent. The ratio between solvent and monomer is preferably in the range from 1:1 to 10:1 by weight.
The temperature to carry out the polymerization stage of the invention generally ranges from about 0xc2x0 C. to about 95xc2x0 C. More preferably, the temperature range is from about 35xc2x0 C. to about 55xc2x0 C. with the higher reaction temperature near the end of reaction. At substantially higher temperatures, side reactions can occur leading to undesirable reaction by-products and at temperatures substantially lower, ice crystals form in the solution. As previously discussed, allowing the reaction mixture to increase above about 50xc2x0 C. results in an increase in the level of backward dimer produced that can be used to catalyze the redistribution reaction.
The process and reaction conditions for the polymerization, such as reaction time, temperature, oxygen flow rate and the like are modified based on the exact target molecular weight desired. The endpoint of the polymerization is conveniently determined with an in-line viscosity meter. Although other methods such as making molecular weight measurements, running to a predetermined reaction time, controlling to a specified endgroup concentration, or the oxygen concentration in solution may also be utilized.
After the end of the oxidative coupling reaction as determined by the desired molecular weight of the PPE, at least one phenolic compound is added to the reaction mixture and allowed to circulate while maintaining the temperature preferably between about 20xc2x0 and about 150xc2x0 C., preferably between about 60xc2x0 and 80xc2x0 C. The reaction mixture is maintained at temperature for about 30 to about 90 minutes, although longer times are possible. During this redistribution step, the flow of oxygen has been preferably halted as the oxidative coupling has been completed. Generally, higher redistribution conversions are obtained under air as opposed to nitrogen.
In the process of the invention, the functionalized phenolic compound is chosen from the following:
A) phenolic compounds with formula 
xe2x80x83wherein R1 represents a hydrogen-atom or an alkyl group and X represents an allyl group, an amino group, a protected amino group (e.g., protected by a tertiary-butyl carbonate), a carboxyl group, a hydroxy group, an ester group or a thiol group, wherein R1 is an alkyl group when X represents an hydroxy group or an ester group, wherein X may be separated from the phenol ring through an alkyl group and wherein the total number of carbon atoms in the alkyl groups attached to the phenol ring is not more than six;
B) bisphenol compounds with formula 
xe2x80x83wherein each X, independently of the other X represents a hydrogen atom, an allyl group, an amino group, a protected amino group (e.g., protected by a tertiary-butyl carbonate), a carboxyl group, a hydroxy group, an ester group or a thiol group, with the proviso that not more than one X group represents a hydrogen atom, R2 and R3 represent an hydrogen atom or an alkyl group with 1-6 carbon atoms and each R4 represents independently of the other R4 a hydrogen atom, a methyl group or an ethyl group;
C) a phenolic compound with at least one of the formulas: 
xe2x80x83wherein m and n have values from 2-20;
D) phenolic compounds with formula 
xe2x80x83wherein x has a value of 12-20 and y has a value of 1-7 or a derivative thereof;
E) multifunctional phenolic compounds with formula 
xe2x80x83wherein R5 represents a hydrogen atom, an alkyl group, an allyl group, an amino group, a protected amino group (e.g., protected by a tert-butyl carbonate), a carboxyl group, a hydroxy group, an ester group or a thiol group; or
F) phenolic compounds with amino groups with formula 
wherein R6 represents independently of one another a hydrogen atom, an alkyl group or a methylene phenol group.
At the end of the redistribution, the functionalized PPE has a lower intrinsic viscosity, and hence a lower molecular weight, than does the PPE at the end of the oxidative coupling reaction. The degree of the decrease is determined at least in part by the amount of phenolic compound utilized and the amount of catalyst, e.g., TMDQ, present. In a preferred embodiment, the functionalized PPE has a weight average molecular weight of at least 1000, preferably between about 3000 and about 70,000 as compared to polystyrene standards. In another preferred embodiment, the functionalized PPE has an intrinsic viscosity of between about 0.05 dl/g and 0.50 dl/g, preferably between about 0.08 dl/g and 0.30 dl/g as measured in chloroform at 30xc2x0 C. The PPE may have a bi-modal distribution of molecular weights.
Preferably after completion of the redistribution reaction, the complex catalyst is chelated to convert the catalyst into a water soluble metal complex. It is also possible to add the chelating agent with the phenolic compound or even before the phenolic compound. In either case, it is preferable to add the phenolic compound within a short time frame after the oxygen flow has been discontinued as the TMDQ will begin redistributing and can become consumed before serving as a catalyst for the phenolic compound.
Many diverse extractants or chelating agents may be used in the practice of the invention to complex with the catalyst. For example, sulfuric acid, acetic acid, ammonium salts, bisulfate salts and various chelating agents may be used. When these materials are added to a PPE reaction solution, the copper-amine catalyst becomes poisoned and further oxidation does not take place. Many different materials may be used but it is preferred to employ those chelating agents that are disclosed in U.S. Pat. No. 3,838,102 (Bennett et al.).
The useful chelating agents include polyfunctional carboxylic acid containing compounds such as, for example, sodium potassium tartrate, nitrilotriacetic acid (NTA), citric acid, glycine and especially preferably they will be selected from polyalkylenepolyamine polycarboxylic acids, aminopolycarboxylic acids, aminocarboxylic acids, aminopolycarboxylic acids, aminocarboxylic acids, polycarboxylic acids and their alkali metal, alkaline earth metal or mixed alkali metal-alkaline earth metal salts. The preferred agents include ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid and their salts. Especially preferred are ethylenediaminotetraacetic acid or a mono-, di-, tri- and tetrasodium salt thereof and the resulting copper complex can be referred to as a copper carboxylate complex.
The chelated metallic catalyst component can be extracted with the water produced in the polymerization reaction by through the use of a liquid/liquid centrifuge. The preferred extraction liquid for use in the process of the invention is an aqueous solution of lower alkanol, i.e., a mixture of water and an alkanol having from 1 to about 4 carbon atoms. Generally from about 1% to about 80% by volume of an alkanol or glycol may be employed. These ratios may vary from about 0.01:1 to about 10:1 parts by volume of aqueous liquid extractant to discrete organic phase.
The reaction media generally comprises an aqueous environment. Anti-solvents can also be utilized in combination with the aqueous media to help drive the precipitation of the copper (I) species. The selection of an appropriate anti-solvent is based partially on the solubility co-efficient of the copper (I) species that is being precipitated. The halides are highly insoluble in water, log K[sp] values at 25xc2x0 C. are xe2x80x944.49, xe2x80x948.23 and xe2x80x9411.96 for CuCl, CuBr and CuI, respectively. Solubility in water is increased by the presence of excess of halide ions due to the formation of, e.g., CuCl2, CuCl3, and CuCl4 and by other complexing species. Non-limiting examples of anti-solvents would comprise low molecular weight alkyl and aromatic hydrocarbons, ketones, alcohols and the like which in themselves would have some solubility in the aqueous solution. One skilled in the art would be able to select an appropriate type and amount of anti-solvent, if any was utilized.
After removal of the catalyst, the PPE containing solution is concentrated to a higher solids level as part of the isolation of the PPE. Precipitation using standard non-solvent techniques typical for PPE having I.V.""s greater than 0.28 dl/g are not generally useful for isolation of low molecular weight PPE due to the small PPE particle size and friability of the particles. Very low yields are obtained with undesirable fractionation of oligomeric species. A total isolation process is preferred for isolating the PPE. As part of the total isolation, a portion of the solvent is preferably removed in order to reduce the solvent load on the total isolation equipment.
Concentration of the PPE containing solution is accomplished by reducing the pressure in a solvent flash vessel while preferably increasing the temperature of the PPE containing solution. Pressures of about 35 to 50 bar are desirable with solution temperatures increased to at least 200xc2x0 C., preferably of at least 230xc2x0 C. A solids level of PPE of at least 55%, preferably of at least 65% or higher is desirable.
The isolation of the PPE is typically carried out in a devolatilizing extruder although other methods involving spray drying, wiped film evaporators, flake evaporators, and flash vessels with melt pumps, including various combinations involving these methods are also useful and in some instances preferred. As previously described, total isolation is preferably from the viewpoint that oligomeric species are not removed to the same degree as with precipitation. Likewise, isolation yields are extremely high and are near quantitative. These techniques require however that the catalyst removal be completed in the prior process steps, as any catalyst remaining in solution will necessarily be isolated in the PPE.
Devolatilizing extruders and processes are known in the art and typically involve a twin-screw extruder equipped with multiple venting sections for solvent removal. In the practice of the present invention, the preheated concentrated solution containing the PPE is fed into the devolatilizing extruder and maintained at a temperature less than about 275xc2x0 C., and preferably less than about 250xc2x0 C., and most preferably between about 185-220xc2x0 C. with pressures in the vacuum vent of less than about 1 bar. The resultant solvent level is reduced to less than about 1200 ppm, preferably less than about 600 ppm, and most preferably less than about 400 ppm.
When using a devolatilization extruder for the total isolation of the PPE, it was found that traditional underwater or water spray cooling of strands of extrudate followed by chopping the extrudate into pellets gave unacceptable results presumably due to the low melt strength and inherent brittle nature of low molecular weight PPE. It was found that special pelletization techniques could overcome these difficulties. Useful techniques include die-face pelletization, including underwater pelletization and flaking, declining angle strand pelletization using water spraying, and vibration drop pelletization with underwater pelletization especially suitable.
It was unexpectedly found that underwater pelletization resulted in a significantly lower color in the PPE as compared to the standard stranding with water/air cooling followed by pelletization techniques. Yellowness index (YI) numbers of less than 30, and even less than 25 are achievable as compared to YI greater than 50 achieved with the standard stranding technique. It should be apparent that the present process affords a method of preparing a PPE with a YI of less than about 30, preferably less than about 25.
The collected PPE pellets can be dried using techniques standard in the art including centrifugal dryers, batch or continuous oven dryers, fluid beds, and the like. Determination of an appropriate set of conditions can be readily determined by one of skill in the art without undue experimentation.
One unexpected advantage of the present invention to make functionalized PPE is using the inherent backward dimer produced in situ by the oxidative coupling reaction to catalyze the redistribution reaction during the polymerization reaction process without a prior isolation of the PPE. This process has advantages for cost reduction simply by reducing the number of handling steps involved. Moreover, the PPE is subject to fewer heat treatments than isolating the PPE followed by re-dissolving the PPE into a suitable solvent for redistribution. The process also affords a method to make a low molecular weight (i.e. PPE with an intrinsic viscosity between about 0.08 dl/g and about 0.16 dl/g) functionalized PPE.
All patents cited by reference are incorporated herein by reference.